The future may not be so bleak after all. MIT digital researcher McAfee (co-author: Machine, Platform, Crowd: Harnessing Our Digital Future, 2017, etc.) ventures that four other horsemen are riding, and perhaps outpacing the familiar apocalyptic ones—namely, “capitalism, technological progress, public awareness, and responsive government.” By his lights, the Club of Rome Limits to Growth report of half a century past was overly Malthusian, and its authors “clearly underestimated both dematerialization and the endless search for new reserves.” The former, the shift to a cyber-based service economy, is easy enough to understand; as McAfee notes, all you have to do is think of the many tools that a modern smartphone replaces, and certainly, fewer resources are required. Still, there are plenty of mountainsides that have gone into that phone, and as for that endless search, McAfee’s enthusiasm for the mineral wealth brought by fracking seems to overlook a few unpleasant externalities. He counters that those externalities, costs that are not immediately evident on a balance sheet, have been allowed for in such market innovations as the buying and selling of rights to pollute, the so-called "cap and trade" program that initially met with great enthusiasm but that, McAfee admits, "aren't enough," particularly in an economic environment that no longer penalizes bad behavior. Even so, assuming his numbers are correct, the author offers hopeful news with the thought that greenhouse gas emissions are falling and that many developed-world economies are using smaller quantities of metals, chemicals, and the like. Given that a fundamental tenet of economics is that scarcity governs the availability and distribution of resources, McAfee’s certainty that the planet is “big enough to contain” all the resources we’ll need “for as long as we’ll need them” might seem to some readers counterintuitive, as he allows. A cogent argument, though climate scientists may find McAfee’s assumptions and faith in market solutions too rosy.